The objective of this study is to show the feasibility of a rapid in vitro test system to individualize and monitor thrombolytic therapy. Despite the recent increase in aggressive thrombolytic therapy, there is a dearth of in vitro blood tests to select the most appropriate thrombolytic agent for a patient requiring thrombolytic therapy. Further, there are no tests to indicate the dose of drug that would be most effective in clot lysis without bleeding complications nor to monitor the efficacy of therapy. This study will adapt a proprietary micro-capillary dynamic flow technique and laser light scattering detection system, developed by Biotrack, to predict and monitor the response of individuals to thrombolytic agents, such as plasminogen activator. Specifically, this study will: (1) establish in vitro relationships between plasminogen activator concentration and clot lysis; (2) investigate variation in and reproducibility of dose responses in different individuals; and (3) establish relationships between plasminogen activator concentration and clot lysis using blood from patients receiving thrombolytic agents.